Paris police searched the headquarters of the national financial prosecutor after a phone-in bomb threat but found no explosives.

A Paris police official says employees are being allowed to return to the building after explosives experts combed the site following the threat Monday. The prosecutor's office is in central Paris, near the Garnier Paris opera house.

The official, who wasn't authorized to be publicly named, says that empty bomb threats are a frequent occurrence in the French capital.

France remains under a state of emergency after a string of deadly Islamic extremist attacks.